A 25-Kg Stone Is Released from Rest and Falls Toward Earth

Multiple Choice

A 2.5-kg stone is released from rest and falls toward Earth. After 4.0 s, the magnitude of its momentum is:

A) 98 kg · m/s
B) 78 kg · m/s
C) 39 kg · m/s
D) 24 kg · m/s
E) zero